Technology for preparing natural gas through sulfur resistant methanation by coal-prepared synthesis gases

Abstract

The invention relates to a technology for preparing natural gas through sulfur resistant methanation by coal-prepared synthesis gases, which is characterized in that coal-prepared synthesis gases is subjected to secondary sulfur resistant transformation and methanation reaction on a molybdenum-based bifunctional catalyst, then is eluted by methanol at low temperature to remove acidic gas, and finally, the Ni-based methanation catalyst is used for performing secondary methanation reaction on unreacted CO and H2 to obtain the excellent natural gas product. The technology for preparing natural gas has the advantages of simple process flow, less equipment investment, low comprehensive energy consumption and excellent natural gas product.

Description

technical field [0001] The invention belongs to a process for producing natural gas from coal, in particular to a process for producing natural gas through sulfur-resistant methanation of synthetic gas produced from coal. Background technique [0002] my country is rich in coal, poor in oil and low in gas, and the proportion of natural gas consumption is far lower than the world average. In recent years, with the rapid increase of natural gas demand in my country, the gap between domestic natural gas supply and demand has gradually increased, which in turn has restricted the steady and rapid development of my country's national economy. Coal-to-natural gas is a technology that uses coal as raw material to produce natural gas. It can convert coal into a clean fuel CH that is convenient for long-distance transportation. 4 , is an important way to optimize the domestic energy structure, alleviate the contradiction between supply and demand of natural gas, and realize the effic...

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Problems solved by technology

Although coal-to-natural gas is the best choice for coal cleanliness and optimal utilization, there are still many problems in the above-mentioned industrial coal-to-natural gas technology due to the limitation of methanation nickel-based catalysts: (1) The low-temperature methanol washing makes the synthesis gas have to undergo "thermal (transformation) )-cold (methanol washing)-heat (methanation)-cold (cooling compression)", the temperature has been varied from 300 to 400°C to -40°C for many times, greatly increasing equipment investment, energy consumption and operating costs; ( 2) The separate sulfur-resistant conversion unit not only increases equipment investment and energy consumption, but also due to the low heat release of water vapor conversion, when the syngas temperature and water vapor content fluctuate, it often encounters the phenomenon that the conversion temperature is too low , so that the organic sulfur in the synthesis gas cannot be completely converted into inorganic sulfur, thereby affecting the subsequent sulfur recovery efficiency; (3) Methanation is a strong exothermic reaction. Dilution will greatly increase the cycle equipment investment and cycle energy consumption

The inventors of this patent have further researched and found that when shift and methanation are carried out simultaneously under the dual-function catalyst, three reactions of methanation, water vapor shift and reverse water gas shift inevitably occur, while the syngas prepared by the existing coal gasification technology contain a lot of CO 2 , especially in the synthesis gas of crushed coal pressurized gasification mostly used in coal-to-natural gas technology 2 The volume content is as high as 28%, and after conversion and methanation, CO 2 content will further increase, a large amount of CO 2 It will lead to the occurrence of reverse water shift reaction, which will greatly reduce the conversion rate of CO. After the acid gas is eluted with low-temperature methanol, there are still a large amount of unconverted CO and H in the product gas. 2 Gas, which affects the quality of natural gas and limits its industrial application

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